They were two of five students at Rouse Hill Anglican College to sit the mathematics extension 1 (3 unit) exam on Wednesday, seeing the HSC a stepping-stone to a career based on their long-term love of numbers.

Both said the exam was harder than expected and they were pushed for time.

``Time was an issue and I didn't complete the paper,'' Varisha said. However, she was confident with her performance in the mathematics 2 unit exam the day before.

Lloyd Windrim, 18, of Kellyville, who attempted five of the seven questions in the extension paper said he was unsure of his performance.

He was the only student at the school to attempt the mathematics extension 2 (4- unit) paper the day before and hoped his preparation would aid him in the 2 unit exam.

Varisha will sit the chemistry and legal studies exams this week and hopes for an ATAR over 85. She would like to study for a bachelor of commerce at Macquarie University or accounting at UTS.

Lloyd said his hardest exams were still to come, with chemistry, physics and economics this week.

``It's important to understand the HSC is not the be all and end all,'' he said.

``If I do the best I can, it will be all right,'' he said.

He is aiming for an ATAR of 92 and to complete a bachelor of engineering at Sydney University.